The present invention generally concerns a galvanic primary cell having a cylindrical metal casing as the negative electrode, a depolarization electrode arranged concentrically around a carbon conductor rod, a separator between the electrodes, and an electrolyte.
Numerous dry cells of this general design are known. In the predominant round-cell type, the negative electrode takes the form of a metal casing, preferably made of zinc, which also serves as the cell housing. In conventional cell designs, this metal casing is then wrapped in a cardboard sleeve, or is simply provided with a label. In leakproof cell designs, the metal casing (together with its contents) is slipped into a sheet-metal covering, with an insulating sleeve placed between these two structures.
Regarding the top of the resulting housing, many designs have been proposed which are particularly directed to preventing desiccation of the cell during storage. Wax, bitumen, or similar substances are often used for sealing purposes. In German Pat. No. 1,114,868, the efficiency of a plastic sealing substance made of bitumen is increased by means of an impervious washer made of wax-impregnated cardboard which is placed between the sealing substance and the cover of the cell.
These and other such arrangements have the disadvantage that they require either considerably expensive production and/or peripheral equipment (heated casings and conductors, metering pumps, cooling lines, etc.) or high uniformity in the prefabricated insert pieces which are used. Moreover, such components must often occupy a considerable volume, thus taking up space at the expense of the active cell components. Lastly, sealing systems of this type often undergo changes over long periods of storage, leading to a deterioration in storage quality, and therefore serviceability, which can be prevented only by employing very costly supplementary measures.